Methods of speeding up seed germination have been known for many years. Methods involving partial hydration of the seeds followed by drying back to the original moisture content are sometimes referred to as "Seed Hardening". Typically this has involved taking the seeds through a number of wetting and drying cycles. Seed priming can be carried out by partial hydration of the seeds by contact with osmotic solutions after which the seeds may be dried back to their original water content. On a small scale seeds can be primed by placing them on absorbent paper saturated with the osmotic solution. In principle seeds can be primed on a large scale by immersing them in the aerated osmotic solution but in practice this is difficult to achieve because the osmotic solutions tend to be viscous and to froth when aerated.
No method of seed priming has yet been found which is sufficiently convenient when carried out in bulk and sufficiently controllable, reproduceable and efficacious to be employed on a large scale in practice.
Known methods of contacting seeds with liquid for purposes other than seed priming are not suitable for use in priming seed. For instance, British Patent Specification No. 1382262 discloses germinating or sprouting seeds such as mustard and cress in a rotating drum into which water is sprayed and from which water drains form recycling. Such direct application of water to seeds will not produce a sufficiently even imbibing of water to be controllable to produce seed priming rather than prompt germination of at least a proportion of the seeds.
Similarly, the process of condensing a mixture of water vapour and pesticide vapour directly on to seeds described in DE-C-1091791 would not be controllable to lead to sufficiently even imbibition of just a sufficient quantity of water to produce seed priming. The process described is for applying pesticides to cereal crop grains, which are large compared to vegetable crop seeds such as carrot, onion and sugar beet for which an acceptable seed priming method is needed. Accordingly, the quantities of water which are to be applied in the method taught in DE-C11091791 are too small in proportion to the mass of the cereal grains to produce seed priming. Applying a seed-priming amount of water by such a method could not be controlled to avoid inducing prompt germination of a proportion of the seeds.
Similar comments apply to all the previously prepared systems in which water is applied directly to seeds as a spray or vapour as a carrier for disinfectants, pesticides, coating materials or the like.